The BSRIA Topic Guides are designed to be an at a glance publication introducing readers to key industry topics and suggesting further reading. BSRIA’s Information Centre is relaunching them with the aim of providing an introduction to key topics in the industry providing readers with an understanding of the area and how they can learn more. A new addition to the topic guides will be a feature by a BSRIA expert on the subject, offering a fresh insight. The airtightness topic guide features an insight into the legislation by our expert David Bleicher.

BSRIA’s Information and Knowledge Manager Jayne Sunley said ‘The topic guides are a great way of providing members and non-members alike with good information that will hopefully clarify some of the questions they have about topics they are new to, they’re not designed to be an all-encompassing guide but rather a starting point for anyone looking to learn more. The addition of the expert insight is just a way of showing readers that there is more to the topic than they might have first thought’.

Indoor Air Quality is a slightly vague concept to most people. When asked they tend to adopt the Goldilocks principle. Not too hot, not too cold, not too damp, not too dry. This reflects the fact that for many generations now we have had the means to control our home and work environment with comparatively little discomfort and little attention being required.

However the golden age of low cost energy and apparently limitless resources seems to be coming to an end. Sustainability is the order of the day. We are all waking up to the real value of energy and the environmental cost involved when linked to our population growth. One cost is the realisation that in cities and near busy roads in the UK there is no longer such a thing as clean fresh air.

We all breathe air to live and if it is polluted or carries airborne diseases we can fall ill as a result. Airborne hazards such as Carbon monoxide or longer term indoor threats like Radon release are sometimes a problem but the toxic fine combustion particles mainly from traffic emissions and some power stations are the major health risk to the public at large.

Technology to the rescue, if we can’t control the weather and have trouble on a national level controlling air pollution then the solution is we can at least try is to control Indoor Air Quality. Ventilation is needed into buildings to replenish used Oxygen from the air and displace the Carbon Dioxide we all exhale.

There has been concern expressed that in the urgent quest for energy savings in large building HVAC systems engineers have been turning off or turning down plant to save energy at the expense of poor building Indoor Air Quality.

A useful European study called Healthvent has recently produced a report that attributes the levels of Burden of Disease for Indoor Air on indoor sourced pollutants and outdoor sourced pollutants respectively. The ratio shows that approximately twice as much BOD can be shown to come from outdoor sourced pollution.

To save building energy losses it has been usual practice to make building envelopes as well sealed as possible as shown by BSRIA testing. This also has the added benefit of helping stop ingress of outside sourced air pollution into the building. Healthvent identified three strategies to reduce outdoor sourced air pollution coming into the building.
1. Optimal dilution using ventilation
2. Effective Air Filtration to reduce PM2.5 by 50%
3. Source control of pollution

Effective Air Filtration was shown to be the easiest measure to implement and give the best reduction of incoming pollution with minimum effort.

Anybody can now access through the internet information on air pollution levels in their locality. There is a national monitoring network run by DEFRA and the local authorities. The Kings College website even allows Londoners to enter their post code and directly get a map of historic readings on their doorstep(example below)

The recent study by Rob Beelen and his team on PM2.5, published in The Lancet, estimates that for every increase of 5 microgrammes per cubic metre (5 µg/m3) in annual exposure to fine-particle air pollution (PM2·5), the risk of dying from natural causes rises by 7%. A simple calculation indicates a routine increase in the mortality rate in central London of over 20% as a result of high levels of PM2.5 mainly from traffic emissions.

Natural causes of death in this instance can be respiratory and cardio vascular disease and recent analysis of data by the Campaign for clean air in London has highlighted that air pollution is one of the exposure categories causing all the top four male death categories and four of the top five female death categories in London i.e. Ischaemic heart diseases; Malignant neoplasm of trachea, bronchus and lung; Chronic lower respiratory diseases; and Cerebrovascular diseases.

It can be seen that the evidence is now compelling and action is now required both at a national level and on a personal level to ensure the air we all breathe is clean and healthy. Some measures such as effective air filtration and air sealed buildings can mitigate exposure to this air pollution in the short term.

Peter Dyment is Air Quality and Energy Consultant at Camfil Ltd (BSRIA Member). Camfil Ltd also has two other excellent sites for readers:

BSRIA has always been in the business of measuring, whether it is a physical quantity such as temperature or pressure, a market assessment such as volume of product imported to a given country or a softer, more management-orientated value such as a benchmark or satisfaction score. Measuring is a fundamental characteristic of our industry’s operations and it is in BSRIA’s DNA.

The need for accurate and more comprehensive measurement has been increasing in response to the revolution that is the low carbon agenda. Revolution is no idle description either. In just over a decade, carbon signatures of new buildings have been required to fall to “nearly zero” – yet few owners were even aware of their building’s operational carbon use at the start. In looking backwards over the past few years, I think BSRIA can be proud of its role in promoting the increased use of through-life measurement embedded in processes such as Soft Landings and the associated building performance evaluations.

There is another BSRIA process that is associated with the collection of measurements. This is the process that turns detailed, often randomly accumulated and frequently disconnected data and information into documents that can be used by our members to guide them in their work. A couple of decades ago this process was greatly enhanced by the availability of a managed construction research programme that not only contributed funds from central government but much more importantly brought focus and long term stability to the accumulation of knowledge. This stability was crucial since it enabled individuals to establish research skills and careers with enduring value to the sector they served. Loss of this programme has also resulted in a loss of cohesion between frontline companies willing to collaborate within the longer term research process.

There is a however a new kid on the block that may be about to revolutionise the traditional measure/analyse/publish process that has dominated research and guidance in our sector.

As disruptive technologies go, Big Data has managed to remain under the public radar quite well until the recent disclosures of the USA “Prism” project. Under Prism, colossal quantities of data harvested from both open and private sources are analysed to identify supposed threats to homeland security. It is the use of automatic analytics software combined with large arrays of sophisticated new sensing technologies that makes Big Data techniques so intriguing for the built environment sector.

By way of example, consider the problem of maintaining comfortable temperatures in a space. Traditionally we have used lab research on volunteers to establish what “comfort” requires. Ole Fanger took years to generate his widely used algorithms but they still do not cover all the possible variables that affect perceived comfort. We now use a thermostat, with a setpoint guided by Fanger, and assume that all is well with our occupants. In the new paradigm, cameras utilising facial recognition software will be capable of spotting yawning (too hot, too much CO?) or sluggish activity (too cold). This data is available for every worker in a given space and a “voting” system used to optimise comfort over the group.

But of course there is more. This data could be available from many sources in a Prism type environment. There would now be the potential to mine the data to establish new benchmarks feeding back to the design process that can be tailored to the particular activity type. Schools, offices, homes and shops each can be analysed not just to establish a single setpoint value but to understand in great detail the envelope or distribution of responses. At last, proper large scale data sets can aid our work – and most of what we need to do this is already available through installed BEMS.

There is one further gain possible from this approach. Traditional academic research leading to refereed papers and thence to institutional guidance can take half a working lifetime to complete. Big Data results can be achieved in hugely reduced timespans. Take the case of adverts you see on Google – these are tailored specifically to you based on purchase decisions you may have only made via unconnected sites a few hours earlier. Scary but true.

Big Data is where BIM, Smart Cities, performance contracting and responsive design meet. It challenges all the preconceptions of professional codes, cuts swathes through the notion of privacy and opens up “our” market for knowledge to an entirely new set of competitive players. The next decade is going to be seriously exciting and I am sure BSRIA will remain strong to its ethos of Measuring and Managing in this startling new environment.

“From a standing start in 2006 to today, the builders have grasped the importance of air tightness testing as a proxy for quality of construction and the contribution good airtightness makes to energy efficiency” Mike Smith, Engineering Director

The rapid adoption of airtightness testing and the ability of the industry to achieve the right result first time in 89% of tests is one of the success stories of the UK construction industry over the past decade. The BSRIA Compliance team tested over 10,000 dwellings and 720 non-dwellings in 2012 and found the average dwelling airtightness value was 4.89 m3/(hr.m2) envelope area at 50 Pa (against a maximum regulatory value of 10 m3/(hr.m2)).

From a standing start in 2006 to today, the builders have grasped the importance of airtightness testing as a proxy for quality of construction and the contribution good airtightness makes to energy efficiency. The testing itself is rigorous, robust and, arguably, now at a very low economic price. It has respectability provided by UKAS accreditation for non-dwellings testing, the training of testers and, in the case of dwelling testing, registered testers through the Airtightness Testing and Measurement Association (part of the British Institute for Non-Destructive Testing).

The mantra should be “Build tight, ventilate right”. As fabric standards improve, driven on further by the 2013 Building Regulations, the role of passive and mechanical ventilation systems increases in importance. Unfortunately in the world of unintended consequences, we are seeing dwellings achieving better airtightness values than the designer intended which of course means less air leakage (and associated energy waste), but this is only useful if the designed-in ventilation systems can cope with these outcomes. In a nutshell the infrastructure supporting domestic ventilation engineering has not developed at the same pace as the improvement in building airtightness.

There is of course significant current activity to help remedy this problem but, as is so often the case, we are now on the back foot with increasing numbers of examples of poor installations and the inevitable questioning of the value of mechanical ventilation solutions.

The systems we are talking about are not complex but they are sensitive to errors. What is missing is not so much the technology or science but the widespread creation and adoption of proper codes of practice. Mechanical ventilation (MV) systems and the more complex MV heat recovery (MVHR) systems have to be site tested to ensure they are extracting and supplying appropriate amounts of ventilation. In the course of its compliance testing BSRIA is seeing two main kinds of problems.

The first is the performance of the specified equipment in a given situation, i.e. that the fan is correctly selected to match both the actual application and the inherent system losses that the system components will introduce. In simple terms this comes down to understanding the resistance characteristics of ductwork and its routing and the resistance of terminal units both inside and out. There is a widespread misunderstanding that ventilation fan outputs are usually quoted with outputs measured in “free air”. In reality they have to overcome backpressures from fittings. Even where kits are bought we see alternative terminal units used, usually to meet architects demands for aesthetics.

The second is the actual installation of the associated ductwork where there is a very poor understanding of the dramatic effect on performance that can arise from bad workmanship.

In a recent case BSRIA found approximately one metre of flexible ductwork that had been stuffed into the cavity wall for a straight through the wall installation that is approximately 300 mm thick. An additional 100 mm dogleg had been introduced on site to match the actual positioning of a porch structure. The result was a lot of fan noise with almost zero movement. The fan, when bench tested with zero back pressure, had a performance of 22 l/s, the designed performance including the ducting was 20 l/s however the actual performance was 5 l/s.

As part of the “catch up” in dealing with the rapid rise in the use of domestic ventilation we have identified that the act of measuring MVHR performance using published guidelines will give false results if the correct equipment or correction factors are not used. There is an easy remedy but not widely used at present. The automatic volume flow meter with pressure compensation – more commonly known as a “powered diff” will provide an instantaneous and accurate value. A more common hooded anemometer will impose a back pressure on the terminal, ducting and fan under test and the readings must be corrected (post use) specifically for both the anemometer model and the actual fan under test. More detail on this can be found in BSRIA’s “Domestic Ventilation Systems – a guide to measuring airflow rates – BG46/2013”.

And all of this is compounded by a lack of thinking regarding operational needs, limited controls, and poor instructions to the user, especially on what maintenance is required to keep performance at its peak.

So, airtightness demands have led to unforeseen consequences and something of a reaction against the use of mechanical ventilation. What then can be done to avoid making the same mistakes on other systems and concepts?

With fabric issues now largely dealt with in the Building Regulations it is likely that new focus will fall on the efficiency and operation of the MEP services in dwellings. If modelling and measuring the thermodynamics of a brick wall is difficult imagine how complex a multivalent heating system is going to be! And before being put into use, these complex integrated systems will need commissioning and possibly proving as well.

The Zero Carbon Hub has recognised that we will need to devise new test methods and regimes that, for example, will evaluate how the solar thermal collector performance meets expectations when linked with the ground source heat pump system that serves hot water generation, underfloor heating and thermal storage, in concert with a biomass boiler or room heater. Before regulation stimulates the market we need to have good practice guidance and proven on-site commissioning and test processes in place. This work is urgent and needs significant central support. With the next revision of Part L expected for 2016 – this time aimed at achieving zero (or nearly) carbon homes, time is not available to embark on a protracted negotiation with innumerable and varied industrial interests. Certainly industry’s support will be available but only for a properly directed and centrally funded programme.

If we fail to put into place a mechanism to improve the on-site verification of performance of new systems we will only have ourselves to blame for the next set of well publicised “failures to launch” and the consequent set back of achieving national aims.

About Us

BSRIA is a test, instruments, research and consultancy organisation, providing specialist services in construction and building services.

We're a non-profit distributing, member-based association, founded in 1955 (owned by The Building Services Research and Information Association). Our Head office is in Bracknell (UK), with regionally based airtightness testers in the UK and offices in France, Spain, Germany and China.

Contact Us

House Rules

We reserve the right to remove comments that we feel are inappropriate. In particular, please do not post anything that may be: irrelevant, too long (over 200 words), offensive or othewise objectionable, unlawful, spam or marketing.